1. ILCDR08
10 July 2008
Plan of measuring cloud density in the solenoid field and in the quadrupole field
K. Kanazawa (KEK)

2. Contents Density measurement with solenoid field.
Density measurement in a quadrupole magnet
Summary

3. Density measurement with solenoid field (1)
The Point
Given a solenoid field and the position of detection, the energy of measured electrons is automatically selected (=the volume is automatically defined).
The detector in a chamber wall can catch high energy electrons produced near a beam.
Vacuum chamber design
Groove
Monitor used without solenoid field
Monitor used with solenoid field

4. Density measurement with solenoid field (2)
Parameters
Bunch size
x = 0.434mm
sy = 0.061mm
sz = 6mm
Number of positron in a bunch = 7.5x1010 (1.2mA)
Solenoid field = 50 Gauss
Simulation to check the idea (Fukuma)
Orbits of kicked electrons near a bunch
Orbits that reach the detector
detector
detector

5. Density measurement with solenoid field (3)
Simulation by Fukuma
Only these electrons reach the detector.
Starting points of electrons that enter the detector
Energy range
+10 16
Y[mm] 8
E[keV]
Beam 8
-10
-10
+10
X[mm]
X[mm]

6. Density measurement with solenoid field (4)
Inside of the chamber
groove

7. Density measurement with solenoid field (5)
Main
Solenoid
Compensation
Solenoids
Chamber with detectors

8. Density measurement in a quadrupole magnet (1)
Electrons accelerated by a bunch along X-axis reach the detector.
Electrons accelerated with small angle to X-axis moves spirally around X-axis losing their energy along X-axis to the spiral motion.
Electrons with sufficient energy and direction close to X-axis reach the detector.
With the help of simulation detector current is converted into the density near beam.
X-axis
Detector

9. Density measurement in a quadrupole magnet (2)
Whole view
Detector

10. Summary
By catching electrons interacted with a bunch, it will be possible to estimate the electron cloud density near the bunch in a magnetic field.
The trial of measuring cloud density in the solenoid field and in the quadrupole field will be carried out this November at KEKB LER.
Thank You!